JP2017114384A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can achieve both improvement in snow traction performance and improvement in external damage resistance.SOLUTION: In a pneumatic tire 1, at a tread part 2, sipe parts 30 are formed at a plurality of land parts 20 partitioned by a groove part 10 which includes a plurality of circumferential grooves 11 extending in a circumferential direction R, a plurality of center lateral grooves 12 and shoulder lateral grooves 13 extending in a width direction W, lug grooves 14, center land part slits 15, and shoulder land part slits 16. When a length constituent in a width direction per unit area of an edge in a tread surface 2a of the groove part 10 is defined as a width-directional constituent LED, a length constituent in a circumferential direction per unit area of the edge in the tread surface 2a of the groove part 10 is defined as a circumferential directional constituent CGD, and a length constituent in the width direction per unit area in the tread surface 2a of the sipe parts 30 is defined as a width-directional sipe constituent LSD, the width-directional constituent LGD is larger than the circumferential directional constituent CGD and the width-directional sipe constituent LSD.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  Conventionally, pneumatic tires for light trucks have a higher internal pressure and load than passenger car tires, and in order to ensure wear resistance, air permeability is suppressed to prevent a decrease in block rigidity or heat generation. The groove shape is taken into consideration.

  For example, in Patent Document 1, a plurality of block portions are partitioned by a plurality of circumferential grooves extending in the tread portion in the circumferential direction and a plurality of width direction grooves intersecting the tread portion, and shallow grooves are formed in the block portions. It is disclosed that a zigzag sipe is formed on the groove bottom of the shallow groove to suppress the opening of the shallow groove, thereby improving the rigidity of the block portion and improving the wear resistance. In Patent Document 2, a plurality of block portions are defined by a plurality of circumferential grooves extending in the circumferential direction of the tread portion and a plurality of width direction grooves intersecting the tread portion, and the average void ratio in the tread portion is limited. Thus, it is disclosed that air permeability is secured and heat generation is suppressed.

  On the other hand, when securing traction performance on a snowy road (hereinafter referred to as snow traction performance), it is known to form a large number of sipes in a block portion. However, when a large number of sipes are formed, the rigidity of the block part is likely to be greatly reduced. Especially in a pneumatic tire for a light truck with a high internal pressure and load, the block part is likely to be chipped and cracked, and is resistant to trauma. Invite worse.

JP 2006-160195 A Special table 2014-521548 gazette

  This invention is made | formed in view of the said subject, and it aims at providing the pneumatic tire which can make the improvement of a snow traction performance and the improvement of damage resistance compatible.

  The present invention comprises a plurality of land portions defined by a plurality of groove portions including a plurality of circumferential grooves extending in the circumferential direction and a plurality of width direction grooves extending in the width direction, and at least one sipe is formed in the land portion. A circumferential length per unit area of the edge of the tread surface of the groove portion, wherein the length component in the width direction per unit area of the edge of the tread surface of the groove portion is a width direction groove component The width component is a circumferential groove component, the length component in the width direction per unit area on the tread surface of the sipe is a width direction sipe component, and the width direction groove component is the circumferential groove component and the width direction sipe component. It is characterized by being larger than.

  The circumferential groove and the width direction groove are cast by a tire vulcanization mold, and the groove width (for example, 2.0 mm or more, more preferably 2. 5 mm or more), for example, a main groove extending in the tire circumferential direction, a lug groove extending in the tire width direction, and a slit. A sipe is a tire vulcanization mold that is molded without casting (for example, cutting with a sipe molding plate), and a groove width (for example, 2) that allows a groove wall to be easily closed when grounded. 0.0 mm or less, preferably 1.5 mm or less). Further, the circumferential direction means the tire circumferential direction, and the width direction means the tire width direction. The land portion includes blocks and ribs.

  According to the present invention, since the widthwise groove component is larger than the circumferential groove component, it is easy to secure the widthwise edge component in the tread surface by the edge portion formed between the groove portion and the tread surface, thereby improving the traction performance. Can be improved. In particular, it is easy to ensure traction performance on snowy roads, and is excellent in snow traction performance. Accordingly, since it is not necessary to form a large number of sipes in order to improve the traction performance, it is possible to suppress the deterioration of the damage resistance of the land portion due to the sipes. Therefore, both improvement in snow traction performance and improvement in trauma resistance can be achieved.

  A circumferential length component per unit area of the edge on the tread surface of the sipe is defined as a circumferential sipe component, and the width sipe component is preferably larger than the circumferential sipe component.

  According to this configuration, it is easy to secure the edge component in the width direction due to sipes, and the snow traction performance can be further improved.

  The circumferential groove preferably extends in a zigzag shape so that the see-through void is zero.

  The see-through void means a ratio in which no land portion exists when the circumferential groove is viewed in the tire circumferential direction. According to this configuration, since the edge component in the width direction of the circumferential groove can be increased, the snow traction performance can be further improved.

The widthwise groove component is preferably 0.010 mm / mm ² or more and 0.040 mm / mm ² or less.

According to this structure, since a groove part has a width direction groove | channel component moderately, a deterioration of damage resistance can be suppressed, improving a snow traction. When the width direction groove component is less than 0.010 mm / mm ² , the traction performance tends to be insufficient. When the width direction groove component is larger than 0.040 mm / mm ² , the rigidity of the land portion is easily lowered, and the effect of suppressing the deterioration of the trauma resistance is reduced.

  Regarding the grounding shape, the effective grounding area is 65% to 75% of the total area of the grounding shape, and the circumferential grounding length at the widthwise grounding end is the circumferential grounding length on the tire equator line. It is preferably 75% or more and 85% or less.

  The effective ground contact area means the area of the part that contacts the road surface. Specifically, the ground contact area (land part) except for the void part (gap part) due to the groove or the like from the entire area of the ground contact shape. Means. According to this configuration, an appropriate ground plane shape can be ensured while achieving both improvement in snow traction performance and improvement in trauma resistance, thereby suppressing deterioration in handling stability and uneven wear resistance.

  The pneumatic tire according to the present invention can achieve both improvement in snow traction performance and improvement in trauma resistance.

The meridian sectional view of the pneumatic tire concerning one embodiment of the present invention. The top view which expands and shows a tread pattern. FIG. 3 is a partially enlarged view of the basic pattern of FIG. 2 schematically showing a width direction groove component. FIG. 3 is a partially enlarged view of the basic pattern of FIG. 2 schematically showing a circumferential groove component. FIG. 3 is a partially enlarged view of the basic pattern of FIG. 2 schematically showing a width direction sipe component and a circumferential direction sipe component. FIG. 3 is a partially enlarged view of the basic pattern of FIG. 2 schematically showing all sipe components. The top view which expand | deploys and shows the tread pattern which concerns on a modification.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. In addition, the following description is only illustrations essentially and does not intend restrict | limiting this invention, its application thing, or its use. Further, the drawings are schematic, and the ratio of each dimension is different from the actual one. In the following description, the outer side in the tire width direction means the direction from the tire equator line toward the tire width direction end of the tread portion, and the inner side in the tire width direction means from the tire width direction end of the tread portion. It means the direction toward the tire equator line.

  FIG. 1 is a half sectional view in a meridian direction of a pneumatic tire 1 for a light truck according to an embodiment of the present invention, and shows only one side with respect to a tire equator line CL. As shown in FIG. 1, a pneumatic tire 1 includes a tread portion 2 that constitutes a tread surface 2 a, a pair of sidewall portions 3 that extend inward in the tire radial direction from both ends, and each sidewall portion 3, 3. And a bead portion 4 located at the inner diameter end.

  The pneumatic tire 1 includes three carcass plies 5 straddling between the bead portions 4 and 4 via the sidewall portion 3 from the tread portion 2, and on the outer side in the tire radial direction of the carcass ply 5, Two reinforcing belt layers 6 and two reinforcing layers 7 are arranged in this order.

  FIG. 2 is a plan view showing the tread portion 2 of the pneumatic tire 1 in a developed state. As shown in FIG. 2, a groove portion 10 is formed in the tread portion 2, and a plurality of land portions 20 are partitioned by the groove portion 10. The groove 10 includes a pair of circumferential grooves 11 and 11 extending in the tire circumferential direction R, and a center lateral groove 12 and a shoulder lateral groove 13 (width direction) that intersect the pair of circumferential grooves 11 and 11 and extend in the tire width direction W. Groove).

  Here, in the present invention, extending in the tire circumferential direction R means not only when extending in parallel with the tire circumferential direction R but also in a zigzag shape or inclined with respect to the tire circumferential direction R. Those extending in the direction R are also included. Similarly, extending in the tire width direction W is not limited to extending in the tire width direction W, but extends in the tire width direction W in a zigzag shape or inclined with respect to the tire width direction W. Is also included.

  The circumferential groove 11 extends in a zigzag shape in the tire circumferential direction R, and is configured such that when viewed in the tire circumferential direction R, the see-through void, which means a ratio in which no land portion exists, is zero. . The center lateral groove 12 extends in a zigzag shape in the tire width direction W, and communicates between the pair of circumferential grooves 11 and 11. The shoulder lateral groove 13 has an inner end in the tire width direction W communicating with the circumferential groove 11, and the other end extending outward in the tire width direction W communicates with the tire width direction end of the tread portion 2. ing.

  The land portion 20 includes a plurality of center land portions 21 defined by a pair of circumferential grooves 11, 11 and a center lateral groove 12, and a plurality of shoulder land portions 22 defined by the circumferential groove 11 and the shoulder lateral grooves 13. , Is included. Further, the center land portion 21 is formed with a lug groove 14 that extends in a zigzag shape in the tire width direction, and the center land portion 21 is separated from the first center land portion 21A and the second center land portion by the lug groove 14. Further divided into 21B in the tire width direction.

  A center land portion slit 15 and a center land portion sipe 31 are formed in the first and second center land portions 21A and 21B, respectively. The first center land portion 21A will be described as an example. The center land portion slit 15 has an end on the outer side in the tire width direction communicating with the circumferential groove 11, and the other end extending inward in the tire width direction is the first. It terminates in the center land portion 21A. The center land portion sipe 31 extends in a zigzag shape inside the tire width direction W, and the lug groove 14 communicates with the end portion of the center land portion slit 15 inside the tire width direction W.

  In the shoulder land portion 22, a shoulder land portion slit 16, a shoulder land portion first sipe 32, and a shoulder land portion second sipe 33 are formed. The shoulder land portion slit 16 has an outer end in the tire width direction W communicating with an end in the tire width direction of the tread portion 2, and the other end extending inward in the tire width direction W is in the shoulder land portion 22. It ends with. The shoulder land portion first sipe 32 extends inward in the tire width direction, and communicates the inner end of the shoulder land portion slit 16 in the tire width direction W with the circumferential groove 11.

  Further, a plurality of shoulder land portion second sipes 33 are formed in the shoulder land portion 22. The plurality of shoulder land portion second sipes 33 are bent and extend in the tire width direction, do not communicate with any of the grooves 11 to 16 and the sipes 31 and 32, and are formed in the shoulder land portion 22. Yes.

  The tread portion 2 has a ground contact end in the tire circumferential direction R at the center portion in the tire width direction, rather than both ends in the tire width direction W, as shown in FIG. It is configured to have a long grounding shape. Specifically, the circumferential ground contact length L2 of the widthwise ground contact edge at both ends in the tire width direction W is shorter than the circumferential ground contact length L1 on the tire equator line, and preferably the ground contact length L2 is equal to the ground contact length L1. 75% or more and 85% or less.

  Further, the ground contact shape of the tread portion 2 has an effective ground contact area of 65% to 75% with respect to the entire region of the ground shape. In other words, the void ratio in the ground contact shape is configured to be 25% or more and 35% or less.

  In addition, as the groove part 10, what is cast-molded by a tire vulcanization mold and has a groove width that does not easily close the groove wall at the time of ground contact, for example, 2.0 mm or more, more preferably 2 Meaning a groove width of 5 mm or more. That is, the groove portion 10 includes a lug groove 14, a center land portion slit 15, and a shoulder land portion slit 16 in addition to the circumferential groove 11, the center lateral groove 12, and the shoulder lateral groove 13.

  Further, the center land portion sipe 31, the shoulder land portion first sipe 32, and the shoulder land portion second sipe 33 are collectively referred to as a sipe portion 30 in the following description. The sipe portion 30 is formed by a tire vulcanization molding die without being cast (for example, cut-in molding by a sipe molding plate), and has a groove width that allows a groove wall to be easily closed at the time of ground contact. Means, for example, having a groove width of 2.0 mm or less, more preferably 1.5 mm or less.

  In the present invention, the length component in the tire width direction W and the tire circumferential direction R per unit area of the edge portion of the tread surface 2a of the groove portion 10 is defined as the width direction groove component LGD and the circumferential groove component CGD, respectively. The length components in the tire width direction W and the tire circumferential direction R per unit area on the tread surface 2a are defined as the width direction sipe component LSD and the circumferential sipe component CSD, respectively, and further, per unit area on the tread surface 2a of the sipe portion 30. Groove portion 10 and sipe portion 30 are configured to have the following relationship, with the extended length as the total sipe component ASD.

  First, the width direction groove component LGD is configured to be larger than the circumferential direction groove component CGD and the width direction sipe component LSD. Preferably, the width direction groove component LGD is set in a range of 1.2 times or more and 3.0 times or less, more preferably 1.5 times or more and 2.0 times or less of the circumferential direction groove component CGD. Further, the width direction groove component LGD is set in a range of 1.2 times to 3.0 times the width direction sipe component LSD, more preferably in a range of 1.5 times to 2.0 times.

  Second, the width direction sipe component LSD is configured to be larger than the circumferential direction sipe component CSD. Preferably, the width direction sipe component LSD is set in a range of 1.2 times or more and 3.0 times or less, more preferably 1.5 times or more and 2.5 times or less of the circumferential direction sipe component CSD.

The width direction groove component LGD and the circumferential direction groove component CGD are set in a range of 0.010 mm / mm ² or more and 0.040 mm / mm ² or less. Widthwise sipes component LSD and circumferential sipe component CSD ^is set in a range of ^{0.005mm / mm 2 ~0.0035mm / mm 2} . The total sipe component ASD is set to 0.025 mm / mm ² or less.

  As shown in phantom lines in FIG. 2, the tread portion 2 repeats the basic pattern P for each circumferential length A with the region indicated by the tire circumferential direction length A and the tire width direction B as a basic pattern P. By arranging, a tread pattern is configured. In the present embodiment, the basic pattern P is configured to be point-symmetric with respect to the tire equator line CL. Hereinafter, a method of obtaining the width direction groove component LGD, the circumferential direction groove component CGD, the width direction sipe component LSD, the circumferential direction sipe component CSD, and the total sipe component ASD will be described with reference to FIGS.

  3 to 6 are enlarged views showing a part of the basic pattern P in an enlarged manner. In FIG. 2, a quarter region obtained by dividing the basic pattern P into two in the tire circumferential direction R and the tire width direction W is shown. Is shown. In the following description, taking a quarter region of the basic pattern P as an example, how to obtain the width direction groove component LGD, the circumferential direction groove component CGD, the width direction sipe component LSD, the circumferential direction sipe component CSD, and the total sipe component ASD. explain.

  First, the width direction groove component LGD will be described with reference to FIG. As shown in FIG. 3, the length component GLL in the tire width direction W projected in the tire circumferential direction R is obtained for the edge portion (groove edge portion) on the tread surface 2 a of the groove portion 10. In FIG. 3, each GLL is shown as GLL1 to GLL14. Then, the sum ΣGLL of each GLL of the groove portion 10 in the basic pattern P is obtained, and the sum ΣGLL is calculated by multiplying the surface area of the basic pattern P (the tire circumferential direction length A and the tire width direction length B of the basic pattern P). ) To calculate the width direction groove component LGD.

  Similarly, with reference to FIG. 4, the circumferential groove component CGD will be described. As shown in FIG. 4, the length component GCL in the tire circumferential direction R projected in the tire width direction W is obtained for each edge portion (groove edge portion) on the tread surface 2 a of the groove portion 10. In FIG. 3, each GCL is shown as GCL1 to GCL18. Then, by obtaining the sum ΣGCL of each GCL in the groove portion 10 in the basic pattern P and dividing the sum ΣGCL by the surface area of the basic pattern P, the circumferential groove component CGD is calculated.

  Next, the width direction sipe component LSD and the circumferential direction sipe component CSD will be described with reference to FIG. As shown in FIG. 5, the groove center line that bisects the groove width in the tread surface 2a of the sipe portion 30 is projected in the tire width direction W and the length component SLL projected in the tire circumferential direction R, and in the tire width direction W. A length component SCL in the tire circumferential direction R is obtained. In FIG. 5, each SLL is shown as SLL1 to SLL6, and each SCL is shown as SCL1 to SCL12.

  Then, the sum ΣSLL of each SLL of the sipe portion 30 in the basic pattern P is obtained, and the sum ΣSLL is divided by the surface area of the basic pattern P, thereby calculating the width direction sipe component LSD. Similarly, by obtaining the sum ΣSCL of each SCL of the sipe portion 30 in the basic pattern P and dividing the sum ΣSCL by the surface area of the basic pattern P, the circumferential sipe component CSD is calculated.

  Next, the total sipe component ASD will be described with reference to FIG. As shown in FIG. 6, the length SL of the groove center line that bisects the groove width in the tread surface 2a of the sipe portion 30 is obtained. In FIG. 6, each SL is shown as SL1 to SL14. The total sipe component ASD is calculated by obtaining the sum ΣSL of each SL of the sipe portion 30 in the basic pattern P and dividing the sum ΣSL by the surface area of the basic pattern P.

  According to the pneumatic tire 1 demonstrated above, there exist the following effects.

  Since the width direction groove component LGD is larger than the circumferential direction groove component CGD, it is easy to secure the width direction edge component in the tread surface 2a by the edge portion formed between the groove portion 10 and the tread surface 2a, thereby improving the traction performance. It can be improved. In particular, it is easy to ensure traction performance on snowy roads, and is excellent in snow traction performance. Accordingly, since it is not necessary to form a large number of sipes in order to improve the traction performance, it is possible to suppress the deterioration of the damage resistance of the land portion 20 due to the sipes. Therefore, both improvement in snow traction performance and improvement in trauma resistance can be achieved.

  Note that the present invention can be more suitably implemented in a so-called light truck tire used at a tire internal pressure of 550 kPa and a load of 1450 kgf, for example, by increasing the widthwise groove component LGD of the groove 10. The snow traction performance can be preferably improved.

  When trying to secure the edge component in the width direction with a sipe as a main component, it is necessary to provide a large number of sipes.For tires with large inputs, the rigidity of the block tends to be insufficient, and the wear of the land part deteriorates. Chipping and cracking are likely to occur. On the other hand, when the width direction edge component is secured by the groove portion 10, it is easy to suppress a decrease in the rigidity of the land portion 20, and therefore, snow traction performance even when the input is large, such as a light truck tire. It is possible to suppress chipping, cracking, and the like of the land portion while suppressing deterioration of wearability of the land portion while securing the above.

  Moreover, since the sipe part 30 has the width direction sipe component LSD larger than the circumferential sipe component CSD, it is easy to ensure the width direction edge component by the sipe part 30, and can further improve snow traction performance.

  Moreover, since the circumferential groove 11 extends in a zigzag shape so that the see-through void becomes zero, the edge component in the width direction of the circumferential groove 11 can be increased, and the snow traction performance can be further improved.

Further, the groove 10, the width direction groove component LGD is configured to be 0.010 mm / mm ² or more 0.040 mm / mm ² or less. Thereby, since the groove part 10 has the width direction groove | channel component LGD moderately, a deterioration of damage resistance can be suppressed, improving a snow traction. When the width direction groove component LGD is less than 0.010 mm / mm ² , the traction performance tends to be insufficient. On the other hand, when the width direction groove component LGD is larger than 0.040 mm / mm ² , the rigidity of the land portion 20 is likely to be reduced, and the effect of suppressing the deterioration of the trauma resistance is reduced.

  Further, the tread portion 2 has a grounding shape in which the circumferential grounding length L2 at both ends in the tire width direction W is shorter than the circumferential grounding length L1 on the tire equator line, and the effective grounding in the grounding shape. Since the area is configured to be 65% or more and 75% or more of the total area of the ground contact shape, it is possible to secure an appropriate ground contact surface shape while achieving both improvement in snow traction performance and improvement in trauma resistance. , Deterioration of operational stability and uneven wear resistance can be suppressed.

  Further, in the groove portion 10, the center lateral groove 12, the shoulder lateral groove 13, the lug groove 14, the center land portion slit 15, and the shoulder land portion slit 16 extending in the tire width direction have at least one end portion in the tire width direction at the circumferential groove. 11 or the tread portion 2 is open at the end in the tire width direction. Accordingly, when traveling on a snowy road, it is easy to introduce snow from the end in the tire width direction of the circumferential groove 11 or the tread portion 2 into the groove portion 10 extending in the tire width direction along with rolling. Snow is easily discharged to the circumferential groove 11 or the end of the tread portion 2 in the tire width direction. As a result, these groove portions 10 are easily bitten by the snowy road, and the traction performance on the snowy road is further improved.

  FIG. 7 shows a tread portion 102 according to a modification. As shown in FIG. 7, the tread portion 102 is partitioned into a plurality of land portions 120 by groove portions 110 and is configured in a tread pattern different from the tread portion 2 according to the above embodiment. Specifically, a pair of circumferential grooves 111, 111 extending zigzag in the tire circumferential direction, and a plurality of center lateral grooves 112 and shoulder lateral grooves 113 extending in the tire width direction intersecting with the circumferential grooves 111, 111 are formed. Thus, the center land portion 121 and the shoulder land portion 122 are partitioned.

  The center land portion 121 is formed with a widthwise lug groove 114 extending in the tire width direction W, a circumferential lug groove 115 extending in the tire circumferential direction R, and a plurality of center sipes 131 extending in the tire width direction W. Yes. In the shoulder land portion 122, a shoulder lug groove 116 extending in the tire width direction, a plurality of shoulder slits 117 extending in the tire width direction, and a plurality of sipes 132 are formed.

  The shoulder lateral groove 113 is formed to be continuous with the widthwise lug groove 114 at the intersection with the circumferential groove 111. The shoulder lug groove 116 is formed to be continuous with the center lateral groove 112 at the intersection with the circumferential groove 111.

  Also in the modified example, the groove portion 110 is a circumferential groove 111, a center lateral groove 112, a shoulder lateral groove 113, a width direction lug groove 114, a circumferential direction lug groove 115, a shoulder lug groove 116, and a shoulder slit 117, and the sipe portion 130 is As the center sipe 131 and the shoulder sipe 132, the width direction groove component LGD, the circumferential groove component CGD, the width direction sipe component LSD, the circumferential direction sipe component CSD, and the total sipe component ASD are in the same relationship as in the above embodiment. It is configured.

  For the pneumatic tires of Comparative Examples 1 to 4 and Examples 1 to 3 shown in Table 1 below, evaluation tests for trauma resistance, snow traction performance, and wear resistance were performed.

In the pneumatic tire according to Comparative Example 1, and the width direction groove component LGD is set to 0.010 mm / mm ² smaller than 0.012 mm / mm ² which is the lower limit of the above embodiment, the circumferential groove component CGD And it is smaller than the sipe component LSD in the width direction, and LGD / CGD is lower than 1.2.

In the pneumatic tires according to Comparative Examples 2 to 3, the width direction groove component LGD is set to 0.040 mm / mm ² which is the upper limit value of the above embodiment, and from the circumferential groove component CGD and the width direction sipe component LSD. And LGD / CGD is set to 3.3.

  More specifically, in Comparative Example 2, only the width direction groove component LGD is increased with respect to Comparative Example 1, and LGD / LSD is set to 2.7. In Comparative Example 3, the width direction sipe component LSD is reduced compared to Comparative Example 2, and LGD / LSD is set to 4.0. In Comparative Example 4, all components related to sipe are increased as compared to Comparative Example 2, and LGD / CGD is set to 1.3.

The pneumatic tire according to Example 1, the width direction groove component LGD is set to 0.040 mm / mm ² which is the upper limit of the above embodiment, the circumferential groove components CGD and greater than the width direction sipes component LSD LGD / CGD and LGD / LSD are both set to 2.9.

In the pneumatic tire according to the example 2, the width direction groove component LGD is set to 0.030 mm / mm ² which is smaller than that of the example 1, and is larger than the circumferential direction groove component CGD and the width direction sipe component LSD. / CGD and LGD / LSD are both set to 2.0.

In the pneumatic tire according to Example 3, the widthwise groove component LGD is set to 0.020 mm / mm ² which is smaller than that of Example 2, and is larger than the circumferential groove component CGD and the widthwise sipe component LSD. Both LGD / CGD and LGD / LSD are set to 1.3.

  In addition, only the pneumatic tire which concerns on Example 4 regarding all the sipe components ASD is set to 0.026 which exceeds the upper limit 0.024 of the said embodiment.

  Pneumatic tires according to Comparative Examples 1 to 4 and Examples 1 to 3 having a tire size of LT285 / 70R17 and a load index (load index) 121 were evaluated. In the trauma resistance test, the damage state of the tread surface after off-road running of 500 km was evaluated under the conditions that the tire was mounted on a light truck and the tire had an internal pressure of 550 kPa and a load of 1450 kgf. “◎” indicates that no damage has occurred, “○” indicates that minor damage has occurred and is the lower limit of practical use, and “×” indicates that damage that causes practical problems has occurred. Show.

  The snow traction performance was evaluated under conditions according to ASTM snow traction conditions (internal pressure 340 kPa, load 925 kgf). The performance of the remaining Comparative Examples 2 to 4 and Examples 1 to 3 is indexed with the case of Comparative Example 1 being 100, and the higher the index is, the better the snow traction performance is.

  The wear resistance was measured by measuring the amount of wear on the tread surface after running 12000 km under conditions of tire internal pressure 550 kPa and load 1450 kgf while being mounted on a light truck. A case where there is no problem with the amount of wear is indicated by “◎”, a case where it is worn but a level where there is no problem in practical use is indicated by “◯”, and a case where it is a level causing practical problem is indicated by “×”. .

  In the pneumatic tires according to Comparative Examples 2 to 4 where LGD / CGD exceeded 3.0, the wear resistance was “x”. This is thought to be because wear is likely to proceed because the rigidity of the land portion is reduced because the widthwise groove component is excessively large. Further, regarding Comparative Example 4, since the components related to sipe were further increased, the trauma resistance was “x”.

  Regarding Example 1, since LGD / CGD and LGD / LSD are both 2.9, the rigidity of the excessive land portion does not decrease, and both the trauma resistance and the wear resistance have the performance at the practical lower limit level. As a result. In addition, regarding Examples 2 and 3, since LGD / CGD and LGD / LSD are smaller than Example 1, the amount of decrease in rigidity of the land portion is less, and both the trauma resistance and wear resistance are superior to Example 1. As a result.

Further, regarding snow traction performance, Comparative Examples ² to 4 and Example 1 in which the widthwise groove component LGD is set to 0.040 mm / mm ² , which is the upper limit value of the above-described embodiment, are the most excellent on the basis of Comparative Example 1. As a result, Examples 2 and 3 resulted in a decrease in the allowance for improvement in snow traction performance relative to Comparative Example 1 in accordance with the amount of decrease in width direction groove component LGD from 0.040 mm / mm ² .

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 2a Tread surface 10 Groove part 11 Circumferential groove 12 Center lateral groove 13 Shoulder lateral groove 14 Lug groove 15 Center land part slit 16 Shoulder land part slit 20 Land part 21 Center land part 22 Shoulder land part 30 Sipe part 31 Center land part sipe 32 Shoulder land part first sipe 33 Shoulder land part second sipe LGD Width direction groove component CGD Circumferential groove component LSD Width direction sipe component CSD Circumferential sipe component ASD All sipe components

Claims (5)

The tread portion includes a plurality of land portions defined by a plurality of circumferential grooves extending in the circumferential direction and a plurality of groove portions including a plurality of width direction grooves extending in the width direction, and the land includes at least one sipe formed in the air. Tire,
The width direction length component per unit area of the edge in the tread surface of the groove portion as the width direction groove component,
The circumferential length component per unit area of the edge in the tread surface of the groove portion as the circumferential groove component,
The length component in the width direction per unit area on the tread surface of the sipe is a width direction sipe component,
The pneumatic tire in which the width direction groove component is larger than the circumferential direction groove component and the width direction sipe component. The circumferential length component per unit area of the edge in the tread surface of the sipe is a circumferential sipe component,
The pneumatic tire according to claim 1, wherein the width direction sipe component is larger than the circumferential direction sipe component.   The pneumatic tire according to claim 1, wherein the circumferential groove extends in a zigzag shape so that a see-through void becomes zero. The pneumatic tire according to any one of claims 1 to 3, wherein the width direction groove component is 0.010 mm / mm ² or more and 0.040 mm / mm ² or less. Regarding the grounding shape of the tread portion, the effective grounding area is an area of 65% or more and 75% or less with respect to the entire region of the grounding shape,
The pneumatic tire according to any one of claims 1 to 4, wherein a circumferential contact length at a width direction contact end portion is 75% or more and 85% or less of a circumferential contact length on the tire equator line. .

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